Processes for increasing bioalcohol yield from biomass

ABSTRACT

A process for increasing alcohol yield from biomass (the form or agro- or forest residue, grains, hops, etc.), involving multiple hydrodynamic cavitation treatments of biomass filtrate—both before and after fermentation. Carbohydrates extracted from biomass are subjected to a first cavitation treatment to promote additional conversion into carbohydrates. The carbohydrates are then combined with bacterial species and nutrients, and allowed to ferment. The fermentation product is subjected to a second hydrodynamic cavitation treatment to promote further conversion of carbohydrates into bioalcohol. After distillation, the bioalcohol is subjected to a second hydrodynamic cavitation treatment to increase its purity.

RELATED APPLICATION

This application is a continuation-in-part of U.S. application Ser. No.14/100,562, filed Dec. 9, 2013, which is a continuation-in-part of U.S.application Ser. No. 12/484,981, filed Jun. 15, 2009 and Ser. No.12/821,000, filed Jun. 22, 2010 (now U.S. Pat. No. 8,603,198).

FIELD OF THE INVENTION

The present invention is directed to a multi-step process for increasingbioalcohol yield from biomass using hydrodynamic cavitation. Moreparticularly, the present invention is directed to: (1) a process forthe extraction of carbohydrates from biomass using hydrodynamiccavitation; and (2) a process for converting the carbohydrates intobioalcohol using hydrodynamic cavitation.

The present invention uses hydrodynamic cavitation for processingheterogeneous and homogeneous liquid systems via a static mechanicaldevice that creates cavitation in a fluidic flow. The shear forceinduced by the flow and turbulence induced by the radial motions ofcavitation bubbles facilitates synthesis of intermediate and finalproducts in the overall production of biofuels. The method may also findapplication in other areas of fluid processing and other fields ofindustry.

BACKGROUND OF THE INVENTION

Bioalcohol, such as methanol, ethanol, butanol, propanol, etc., may bederived from biological materials, i.e., biomass primarily throughfermentation. Such production can proceeding by typical chemicalprocessing, as is used with natural gas, or by fermentation of sugars.Prior art bioalcohols may be derived from a number of sources, many ofwhich are time consuming and/or cost intensive to produce ormanufacture. The prior art processes for producing bioalcohols wouldbenefit greatly from an improved and more efficient method of producingalcohol.

Existing technologies in processing industries are similar in concept inthat they all require an input of energy to produce a final product. Forexample, some technologies include a pressurized homogenizer, which usesa sequential valve assembly to increase fluid pressure in the materialbeing processed. Such a device requires a large energy input, producinga high outlet pressure, usually in excess of 5,000 psi.

Cavitation is defined as the generation, subsequent growth and ultimatecollapse of vapor- or gas-filled cavities in liquids resulting insignificant energy concentration and release on extremely small temporaland spatial scales. As understood in this broad sense, cavitationincludes the familiar phenomenon of bubble formation when water isbrought to a boil under constant pressure. In engineering and science,the term cavitation is used to describe the formation of vapor-filledcavities in the interior or on the solid boundaries created by alocalized pressure reduction produced by the dynamic action of a liquidsystem.

Hydrodynamic cavitation is essentially generated by a change in bulkpressure in a liquid flow by variation of the velocity of the flowthrough well-defined geometries. In the simplest situation, hydrodynamiccavitation can be generated by forcing or throttling high pressuredischarge from a pump through constrictions such as a venturi or anorifice. In this case, the velocity of the flow increases with reducingflow area causing a concurrent reduction in bulk pressure. If thethrottling is sufficient, the pressure in the flow in the regiondownstream of the constriction may actually fall to or even below thevapor pressure of the medium. This causes the release of dissolved gasin the medium or generation of vapor bubbles in the liquid medium. Thesebubbles undergo oscillation with a recovery of pressure in the regionfurther downstream resulting in a final transient collapse. Theoscillations of the bubbles generate intense microturbulence in themedium causing vigorous mixing.

For a heterogeneous reaction system, this turbulence can create a fineemulsion between phases generating high interfacial area that canenhance the reaction kinetics. At the transient collapse of the bubble,the temperature and pressure in the bubble can reach extremely highvalues (˜3000 K, ˜100 bar or even higher) that can cause decompositionof the solvent vapor entrapped in the bubble resulting in generation ofextremely reactive radicals that can accelerate the kinetics of achemical reaction. The amplitude of the radial oscillation of thecavitation bubble and the intensity of collapse depends on the extent ofvariation in bulk pressure (or the bulk pressure gradient), which ischaracterized by a cavitation number. For a cavitation number equal toor less than 1, the bulk pressure gradient is high enough to causetransient cavitation. As the cavitation number increases above 1, theintensity of radial motion of the cavitation bubbles reduces. Thecavitation bubbles experience small amplitude oscillatory motion, whichcan give rise to intense microturbulence in its vicinity.

Cavitation can occur at numerous locations in a fluid bodysimultaneously and can generate very high localized pressure andtemperature on extremely small time scales, e.g., dozens of nanoseconds.Cavitation also results in the generation of localized turbulence andliquid micro-circulation, enhancing mass transfer—which is a prominenteffect, especially for heterogeneous (either liquid-liquid orsolid-liquid) systems. Thus, mass transfer-limited reactions,endothermic reactions and reactions requiring extreme conditions can beeffectively carried out using cavitation. Moreover, radicals generatedduring cavitation due to the homolytic dissociation of the bonds ofmolecules trapped in the cavitating bubbles or in the affectedsurrounding liquid, result in the occurrence of certain reactions.

The flow essentially undergoes a sudden contraction and expansion thatgenerates essential pressure variation for the in-situ generation andcollapse of either vapor or gas bubbles. As stated earlier, thesebubbles undergo volume oscillations and a transient collapse, which cancreate cavitation effects by intense energy concentration that resultsin extremes of temperature and pressure and also intense convection dueto micro-turbulence and shock waves. However, this effect is seen eitherinside the bubble (of initial size ˜50-100 microns, which is compressedto about 1/10^(th) of its initial size) or in the bulk liquid in closeproximity to the bubble. Thus, the energy concentration created bytransient bubbles is on an extremely small time and temporal scale.

Through these contractions and expansions, the flow may get separatedfrom the walls of the conduit for a high Reynolds number. In this case,there is significant loss in the pressure head of the flow, which ismanifested in terms of generation of turbulence in the flow. Theturbulence creates fluctuations in the bulk pressure at low frequencies(1 to 2 kHz). These turbulent fluctuations are essentially superimposedover the mean pressure of the flow that keeps on increasing with theexpansion of the flow. These fluctuations alter the behavior or patternof radial motion of the cavitation bubble. In this case, the bubbleundergoes an explosive growth followed by a transient implosivecollapse. The cavitation effect produced by these bubbles is severalfolds higher than the bubbles in simple venturies orconverging-diverging nozzles, where such flow separation does not occur.The difference in the cavitation bubble behavior in a orifice flow andin a venturi flow has been studied at length. (VS Moholkar and ABPandit, Chemical Engineering Science, 2001).

In homogenous reactions, both the reagents and products remain in thesame phase. The mechanical or physical effects of cavitation (e.g.,generation of high intensity micro-turbulence) play a smaller part insuch reactions in comparison with the chemical effects of creation ofhigh-energy intermediates. In heterogeneous reactions, cavitationbubbles collapsing at or near the phasic interface undergo asymmetriccollapse, giving rise to high velocity liquid microjets (with velocitiesin the range of 100-150 m/s). These microjets can give rise to severaleffects such as erosion of the surface or fragmentation and sizereduction of the particles. Due to these effects, surface area availablefor the reaction between the phases is significantly increased, thusimproving the rate of reaction. In case of catalytic reactions,microjets assist desorption of products from the catalyst surface, whichhelps in keeping the catalyst surface ‘fresh’ for reaction. Microjetsalso assist desorption of the catalyst poisons attached to the catalystsurface that helps in cleaning of the catalyst. Moreover,adsorption/desorption of the reactants/products on the catalyst surfaceis also facilitated by the microturbulence generated by cavitationbubbles.

TABLE 1 Comparison of energy efficiency for different methods. Time,Yield/energy, Method min Yield, % kJ⁻¹ Acoustic 10 99 8.6 × 10⁻⁵Conventional with stirring 180 98 2.7 × 10⁻⁵ Presented flow-through 899.9 2.6 × 10⁻³

It can be seen from Table 1 that reactions that take place in aflow-through cavitation generator are correspondingly about 30 times and100 times more efficient compared to acoustic cavitation theagitation/heating/refluxing method.

Accordingly, there is a need for a method to carry out heterogeneousreactions that does not require a large amount of energy input. Further,there is a need for such a method that avoids potentially dangerous,high-pressure operation. Furthermore, there is a need for an improvemethod of producing alcohol from biomass that is more efficient and morecost effective. The present invention fulfills these needs and providesfurther related advantages through the utilization of hydrodynamicflow-through cavitation and the chemical and physical reactions andprocess involved.

SUMMARY OF THE INVENTION

The method described herein does not require high energy input as thecavitation device is static, i.e., it does not contain moving parts. Theapparatus simply requires a minimum input fluid velocity and pressure tocreate cavitation in the flow towards the goal of creating new products.The inventive process may also be practiced using a rotor-statorcavitation device.

The present invention is directed to a process for increasing bioalcoholyield from biomass. The process involves providing carbohydratesextracted from the biomass, wherein the carbohydrates contain residualstarches, dextrins, and proteins. The carbohydrates are subjected to ahydrodynamic cavitation treatment so as to promote additional conversionof the residual starches, dextrins, and proteins into carbohydrates. Thecarbohydrates are then combined with a bacterial species and nutrientsto form a fermentation fluid. The fermentation fluid is fermented toform a bioalcohol solution, which bioalcohol solution is then subjectedto an additional hydrodynamic cavitation treatment so as convert anyremaining carbohydrates into bioalcohol. The bioalcohol solution is thendistilled so as to separate out bioalcohol and a fermentation broth. Thebioalcohol is then subjected to a further hydrodynamic cavitationtreatment so as to purify the bioalcohol for food grade production.

The biomass or fermentation substrate may comprise a filtrate ofhydrolyzate containing pentose sugars or hexose sugars obtained fromacid hydrolysis and enzymatic hydrolysis of biomass. In either case, thebacterial species comprise Escherichia Coli, Saccharomyces cerevisiae,Zymomonas mobilis, Lactobacillus buchneri, or Clostridiumacetobutylicum. The further hydrodynamic cavitation treatment of thebioalcohol destroys impurities, precipitates out heavy metals, improvestaste and reduces a smell of the bioalcohol. The impurities may comprisewater, acetaldehyde, acetal, benzene, methanol, fusel oils, non-volatilematter, and heavy metals.

The step of subjecting the bioalcohol to a further hydrodynamiccavitation treatment comprises pumping the bioalcohol through ahydrodynamic cavitation device at a pump pressure of about 60 psi. Thestep of subjecting the bioalcohol to a further hydrodynamic cavitationtreatment comprises passing the bioalcohol through a hydrodynamiccavitation device at least twenty times. It is worth noting here thatsince alcohols are extremely volatile compounds that can evaporate intothe bubbles and undergo thermal dissociation at the point of transientcollapse.

The present invention is also directed to a process for extractingcarbohydrates from biomass through 3 steps, generally, acid pretreatment(for hydrolysis of hemicellulose in biomass to pentose sugars), alkalinepretreatment (for delignification or removal of lignin from biomass) andfinally enzymatic hydrolysis of the cellulose in biomass to hexosesugars. During the acid pretreatment (or hemicellulose hydrolysis) thebiomass solution is subjected to hydrodynamic cavitation. The biomasssolution is filtered to separate the biomass, which is washed and dried.The solution or hydrolyzate obtained after separation of biomass iscomprised of pentose sugars. Next, the biomass is again subjected tohydrodynamic cavitation in an alkaline solution for delignification. Theresultant solution is filtered to separate biomass, which is nowcomprised of mostly cellulose. This biomass is then subjected toenzymatic hydrolysis with hydrodynamic cavitation under milderconditions (due to the sensitivity of the enzymes towards intenseconditions generated by transient cavitation). The solution (orhydrolyzate) obtained after this treatment is comprised of hexosesugars. The two hydrolyzates of pentose and hexose sugars may then belater fermented into alcohol, as discussed above.

A particular process for extracting carbohydrates involves preparing thebiomass for extraction of carbohydrates and forming a first biomasssolution comprising the prepared biomass, water, and acid or an alkali.This first biomass solution is subjected to a first hydrodynamiccavitation treatment at an inlet pump pressure of about 500 psi, whereinacid and/or alkali hydrolysis of the biomass occurs. This firsthydrodynamic cavitation treatment may be separated into two cavitationtreatments—one for acid hydrolysis and another for alkali hydrolysis,with intervening filtration, washing, and drying steps. The firstbiomass solution is filtered following the first hydrodynamic cavitationtreatment, whether as a single process or separate processes, into afirst filtrate and an intermediate biomass, wherein the first filtratecontains extracted carbohydrates. A second biomass solution is createdcomprising the intermediate biomass, water and an enzyme source. Thesecond biomass solution is exposed to a second hydrodynamic cavitationtreatment at an inlet pump pressure of about 50 to 150 psi, whereinenzymatic hydrolysis of the biomass occurs. This second biomass solutionis filtered following the second hydrodynamic cavitation treatment intoa second filtrate and a filtered biomass, wherein the second filtratecontains extracted carbohydrates.

The preparing step comprises wet milling the biomass. Wet millingcomprises mixing fresh biomass and water to form a slurry. This slurryis then homogenized so as to agglomerate gluten particles in the slurry.The homogenized slurry is then conveyed via a buffer tank to a decanter,wherein the slurry is washed, classified, and concentrated. The slurryis then separated into a first product comprised of starch and glutenand a second product comprised of starch and pentosane. The secondproduct is passed to a biomass storage tank consisting of preparedbiomass.

The preparation of the biomass may include washing, drying, choppingand/or grinding the biomass. The biomass may include hops, corn cob,corn stover, cotton stalk, wheat straw, rice straw, sugarcane bagasse,switchgrass, poplar wood, sorghum straw, and/or water hyacinth.

A first biomass solution is formed by combining the prepared biomasswith water, preferably demineralized, and an acid and/or an alkali.Where the first hydrodynamic cavitation process is separated into acidand alkali processes, the acid is added first for hemicellulosehydrolysis and the alkali is added second for delignifiction. In theinstance of sequential acid/alkali processing, after the interveningwashing and drying, the first biomass solution is reformed by addingwater. In both instances, the demineralized water is added in a ratio ofabout 5% to 50% w/v with the biomass. The acid preferably comprisessulfuric acid in the range of 1% to 5% v/v and the alkali preferablycomprises sodium hydroxide in the range of 1% to 5% v/v. This firstbiomass solution is preferably thoroughly agitated to prevent settlingof biomass particles.

During the first hydrodynamic cavitation treatment, acid and/or alkalihydrolysis of the biomass occurs. The first biomass solution ispreferably heated prior to the first hydrodynamic cavitation treatment;such heating by autoclaving, steam explosion or simple heat treatment.For the second biomass solution (after all hydrolysis) the biomass withdemineralized water is prepared with typical concentrations of biomassin the range of 5% to 25% w/v. The enzyme source comprises cellulaseenzymes, or microbes or fungi that release cellulase enzymes, themicrobes comprising Bacillus amyloliquefaciens or Bacillus subtilis andthe fungi comprising Trichoderma reesei. The process includes adjustingthe pH of the second biomass solution to a desired pH for the enzymesource. The intermediate biomass is preferably washed and dried prior tocreating this second biomass solution. The second biomass solution isfiltered to separate biomass particles (which are essentiallydelignified). The biomass is then washed to remove the traces of alkalisolution. During the subsequent hydrodynamic cavitation treatmentenzymatic hydrolysis of the biomass occurs.

Other features and advantages of the present invention will becomeapparent from the following more detailed description, taken inconjunction with the accompanying drawings, which illustrate, by way ofexample, the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate the invention. In such drawings:

FIG. 1 is a perspective view depicting a preferred embodiment of amulti-stage cavitation device of the present invention.

FIG. 2 is a cross-sectional view of the multi-stage cavitation devicetaken along line 2-2 of FIG. 1.

FIG. 3 is a cross-sectional view of the working chamber of thecavitation system taken along line 3-3 in FIG. 2.

FIG. 4 is a cross-sectional view of the vortex element taken along lines4-4 in FIG. 2.

FIG. 5 is a cross-sectional view of one embodiment of a channel in amulti-jet nozzle taken along line 5-5 in FIG. 3.

FIG. 6 is a cross-sectional view of an alternate embodiment of a channelin a multi-jet nozzle taken along line 6-6 in FIG. 3.

FIG. 7 is a flowchart illustrating the processes for extractingcarbohydrates from biomass and converting those carbohydrates intobioalcohol.

FIG. 8 is a cross-sectional view of an alternate embodiment of thecavitation device of the present invention.

FIG. 9 is a cross-sectional view of an outlet portion of the cavitationdevice depicted in FIG. 8.

FIG. 10 is a side, cross-sectional view of the impact pad of thecavitation device of FIG. 8.

FIG. 11 is an end view of the impact pad of the cavitation device ofFIG. 8.

FIG. 12 is a perspective view another preferred embodiment of amulti-stage cavitation device.

FIG. 13 is a cross-sectional view taken along line 13-13 of FIG. 12.

FIG. 14 is a cross-sectional view of the turbulizer disk taken alongline 14-14 of FIG. 13.

FIG. 15 is a cross-sectional view of the radial multi-jet nozzle takenalong lines 15-15 of FIG. 13.

FIG. 16 is a cross-sectional view of the cylindrical body taken alonglines 16-16 of FIG. 13.

FIG. 17 is a side view of the cylindrical body.

FIG. 18 is a close-up view of the front interior working chamber andtoroidal vortex chamber illustrating fluid flow.

FIG. 19 is a close-up view of the back interior working chamber andtoroidal vortex chamber illustrating fluid flow.

FIG. 20 is a cross-sectional view of various forms of the hemi-sphericalbody.

FIG. 21 is a cross-sectional view of another preferred embodiment of themulti-stage flow-through hydrodynamic cavitation device.

FIG. 22 is a cross-sectional view taken along line 22-22 of FIG. 21.

FIG. 23 is a cross-sectional view of a flow orifice used in numericalsimulations of hydrodynamics cavitation processes.

FIG. 24A is a graph illustrating Radius Ratio versus Time of a firstpermutation of a numerical simulation of the cavitation process.

FIG. 24B is a graph illustrating Temperature versus Time of a firstpermutation of a numerical simulation of the cavitation process.

FIG. 24C is a graph illustrating Pressure versus Time of a firstpermutation of a numerical simulation of the cavitation process.

FIG. 24D is a graph illustrating Shockwave versus Time of a firstpermutation of a numerical simulation of the cavitation process.

FIG. 24E is a graph illustrating Microturbulence versus Time of a firstpermutation of a numerical simulation of the cavitation process.

FIG. 25A is a graph illustrating Radius Ratio versus Time of a secondpermutation of a numerical simulation of the cavitation process.

FIG. 25B is a graph illustrating Temperature versus Time of a secondpermutation of a numerical simulation of the cavitation process.

FIG. 25C is a graph illustrating Pressure versus Time of a secondpermutation of a numerical simulation of the cavitation process.

FIG. 25D is a graph illustrating Shockwave versus Time of a secondpermutation of a numerical simulation of the cavitation process.

FIG. 25E is a graph illustrating Microturbulence versus Time of a secondpermutation of a numerical simulation of the cavitation process.

FIG. 26A is a graph illustrating Radius Ratio versus Time of a thirdpermutation of a numerical simulation of the cavitation process.

FIG. 26B is a graph illustrating Temperature versus Time of a thirdpermutation of a numerical simulation of the cavitation process.

FIG. 26C is a graph illustrating Pressure versus Time of a thirdpermutation of a numerical simulation of the cavitation process.

FIG. 26D is a graph illustrating Shockwave versus Time of a thirdpermutation of a numerical simulation of the cavitation process.

FIG. 26E is a graph illustrating Microturbulence versus Time of a thirdpermutation of a numerical simulation of the cavitation process.

FIG. 27A is a graph illustrating Radius Ratio versus Time of a fourthpermutation of a numerical simulation of the cavitation process.

FIG. 27B is a graph illustrating Temperature versus Time of a fourthpermutation of a numerical simulation of the cavitation process.

FIG. 27C is a graph illustrating Pressure versus Time of a fourthpermutation of a numerical simulation of the cavitation process.

FIG. 27D is a graph illustrating Shockwave versus Time of a fourthpermutation of a numerical simulation of the cavitation process.

FIG. 27E is a graph illustrating Microturbulence versus Time of a fourthpermutation of a numerical simulation of the cavitation process.

FIG. 28 is a flowchart illustrating an alternate process for treatmentof the filtrates following extraction of carbohydrates.

FIG. 29 is a flowchart illustrating the processes for wet milling ofbiomass prior to extraction of carbohydrates.

FIG. 30 is a table reporting data on impurities found in bioalcoholbefore and after cavitation processing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed to a device and method for processinga fluidic reaction mixture via a hydrodynamic cavitation process withthe result being the creation of new products. The reaction componentsinside the apparatus are influenced by pressure impulses and otherfeatures of controlled advanced hydrodynamic cavitation. The device andmethod herein described follows the aforementioned chemical reactionsand processes such that the device stimulates cavitation in hydrodynamicliquids to the point where the end result is increased yield and qualityof products.

A multi-step process for increasing bioalcohol yield from biomass usinghydrodynamic cavitation is disclosed herein. More particularly, themulti-step process includes: (1) a process for the extraction ofcarbohydrates from biomass using hydrodynamic cavitation assisted acidpretreatment, alkaline delignification, and enzymatic hydrolysis; and(2) a process for converting the carbohydrates into a bioalcohol usinghydrodynamic cavitation assisted fermentation.

The hydrodynamic cavitation device described herein is highly versatilefor the extraction of carbohydrates from ligno-cellulosic biomass (orthe biomass pretreatment), which is an important and cost-intensive stepin the synthesis of bioalcohol and (alcoholic) biofuels, especiallythrough the fermentation (or biochemical) route. Hydrodynamic cavitationis useful in the pretreatment of biomass prior to synthesis ofbiofuels—primarily through fermentation. Such processing enhances therelease of carbohydrates or sugars from biomass prior to fermentation ofhydrolyzate (comprising of hexose and pentose sugars).

Hydrodynamic cavitation can be applied during pretreatment of thebiomass, especially chemical pretreatment such as with dilute acid ordilute alkali. These pretreatments are applied prior to the enzymatichydrolysis of cellulose in the biomass. The pretreatment has a two-foldpurpose: (1) to break down the shield formed by lignin and removal ofhemicellulose through acid hydrolysis which results in better and higheraccessibility of enzymes to the cellulose during enzyme hydrolysis; and(2) to reduce the degree of polymerization of cellulose with disruptionof crystalline structure, which enhances the yield of the enzymatichydrolysis. The ligno-cellulosic biomass is typically in the form ofagro- or forest residue. Biomass pretreatment is perhaps the most costintensive step in overall bioalcohol and alcoholic biofuel synthesis.Obviously, any advancement of the pretreatment technology would have asignificant impact on the economics of biofuels.

Prior to chemical pretreatment, the biomass is subject to a physicaltreatment such as mechanical comminution (reduction of particle size inorder to increase surface area), steam explosion or autoclaving and/orliquid hot water pretreatment. During these pretreatments, thehemicellulose is partially hydrolyzed by acids released from thebiomass. Hot water can have acidic properties at high temperatures thatassist or catalyze the hemicellulose hydrolysis. These treatments causethe biomass to undergo rapid thermal expansion, which leads to openingup of the biomass particle structure and an increase in pore volume.

The chemical pretreatment is essentially aimed at enhancing thebiodegradability of cellulose by removing the lignin and hemicellulose,and also to decrease the degree of polymerization and crystallinity ofthe cellulose component. The most common techniques that are applied aredilute acid pretreatment for removal of hemicellulose through hydrolysisto pentose sugars and delignification by dilute alkali pretreatment. Inthe dilute acid treatment, several different acids like dilute sulfuricacid, dilute nitric acid or dilute phosphoric acid may be used.

Dilute acid pretreatment results in solubilization of hemicellulosewhile keeping the lignin and cellulose intact, which results inenhancement of enzymatic digestibility of cellulose. In this process,the oligomeric hemicellulosic saccharide can be hydrolyzed (almost tocompletion, depending on processing conditions) into primarily pentosemonosaccharides. Nonetheless, dilute acid may cause degradation of somesugar molecules into furfural. Dilute acid treatment results in a highyield of pentose sugars like xylose. The addition of acid into thereaction mixture could be in homogeneous form or heterogeneous form suchas an ion exchange resin. Recently, some have used Amberlyst-TM (15) ionexchange resin as a catalyst for hydrolyzing carbohydrates frommacroalgae Eucheuma cottonii to extract simple sugars prior tofermentation.

The inventive cavitation device can also be used for the dilute acidpretreatment of biomass to release pentose carbohydrates and sugars. Theaddition of dilute acid (the most widely used acid being the sulfuricacid) gives effective hydrolysis. However, this acid itself hascorrosive effects, and hence, the material from which the cavitationdevice is constructed needs to be suitably selected. Otherwise acorrosion resistant coating such as PTFE can be applied to the walls ofthe flow conduit. The pump used with the hydrodynamic cavitation deviceneeds to have a sufficiently high discharge pressure to pump the processfluid.

For an alkaline pretreatment, various bases are used which primarilyinclude dilute sodium or potassium hydroxide, calcium hydroxide, aqueousammonia or ammonium hydroxide. Alkaline pretreatment results inprimarily delignification of biomass through different chemicalmechanisms such as breakage or ether linkages between aromatic moietiesand side chain elimination. Alternate chemical mechanism are essentiallysaponification of intermolecular ester bonds cross-linking xylanhemicelluloses and other components like lignin. The alkalinepretreatment of lignocellulosic biomass has several beneficial effectssuch as increased internal surface area due to swelling, decreaseddegree of polymerization and reduced crystallinity. Moreover, alkalinepretreatment also disrupts the lignin structure and also separates thelinkages between lignin and carbohydrates. Similar to the dilute acidpretreatment, the alkali can be added to the mixture of biomass andwater before being subjected to the treatment in a hydrodynamiccavitation device.

An alternate method of providing catalyst in the reaction system is tocoat the walls of the conduits with certain metal oxides (especiallyalkali metals such as calcium oxide) or mixed metal oxides (alkali metaloxide+alkaline earth metal oxides, such as calcium oxide+barium oxide orcalcium oxide+barium oxide+strontium oxide). In acid hydrolysis, thewalls could be coated with an ion exchange resin (in the form of apolymer film). These coatings can provide the necessary catalytic effecti.e. supplying of H⁺ or OH⁻ ions needed for hydrolysis. In thisconfiguration, the undesired effects of corrosion due to homogenous acidor alkali catalyst can also be avoided. The turbulence present in thecavitating flow can assist faster and efficient transfer of the ionsgenerated at the walls of the conduit due to interaction of the flowwith the coated catalyst.

Enzymatic hydrolysis is used to separate the glycosidic links in thestarch chains. These processes generally operate nearer to neutral pHlevels than acid hydrolysis and at lower temperatures so they requireless heating. The use of enzymes is very high glucose yields arepossible which will improve the overall starch to ethanol conversion.

Hydrolysis of the biomass (by either acids or enzymes) is essentially amass transfer controlled process. The long chain cellulose moleculespresent in the biomass are less soluble in water than the short chainoligomers formed as intermediates during the hydrolysis. The solubilityof both long and short chain molecules decreases with temperature. Withsufficient and continuous flow of liquid through the reaction mixture(especially in and around the biomass matrix where hydrolysis occurs),the more soluble molecules are removed which facilitates furtherdissolution of less soluble molecules. This process not only enhancessugar recovery but also reduces the degradation of sugars at thereaction conditions. If the more soluble oligomers are not removed, theyare likely to precipitate back onto the surface of the biomass,especially with decreasing temperature of the reaction mixture afterprocessing. Reactive lignin and sugar degradation products can alsopromote reattachment of cellulose, hemicellulose, and their oligomers,as well as, lignin, back to the solid biomass. These components may alsoform complexes with monomeric sugar if not removed.

The occurrence of transient cavitation in the reaction mixture generatesintense microturbulence that removes and refreshes the water in theclose packed biomass matrix. This assists in the efficient removal oflocalized sugar molecules formed within the biomass matrix. Thesonochemical effect, i.e., the generation of highly reactive radicalsdue to the transient collapse of bubbles, may also contribute to alimited extent to the enhancement of sugar or carbohydrate release fromthe biomass. This is, in part, because most of the hydrolysis reactionoccurs through H⁺/OH⁻ ions in the solution provided by the acid/alkali.

Numerical simulations of cavitation bubble dynamics in flow throughconstrictions show the formation of strong microturbulence and highintensity shock waves during the transient bubble motion in cavitatingflow through nozzles, venture, or the like. The exact dimensions of theconstriction are decided by the capacity of the overall unit and maychange with the capacity. In such mathematical models, the vaportransport in the cavitation bubble during radial motion is hypothesizedto be a diffusion limited process. The diffusion limited model is asfollows: The expansion of the cavitation bubble is accompanied by theevaporation of an ever increasing quantity of solvent vapor (water inthe case of biomass hydrolysis) at the bubble wall. These vapormolecules diffuse into the core of the bubble. During the ensuingcollapse phase, the vapor molecules diffuse back out to the bubble walland condense.

In the final moments of bubble collapse, the bubble wall velocitybecomes extremely fast (sometimes even exceeding the speed of sound). Atthe moment of collapse, the time scale of diffusion of vapor in thebubble towards the bubble wall exceeds the time scale of bubble motion.The vapor thus becomes “frozen” or entrapped in the bubble. Due to theextremely rapid motion of the bubble wall, the condensation of the vapormolecules that manage to reach the bubble wall is not in equilibrium(i.e. not all vapor molecules undergo condensation and phase change dueto small accommodation coefficient). This further contributes toentrapment of the solvent vapor in the bubble. The entrapped vapor isthen subjected to extreme conditions of temperature and pressuregenerated at the final stage of bubble collapse, when the bubble size isat its minimum during the radial motion. At these conditions, the vapormolecules undergo thermal dissociation to generate numerous species,some of which are radical species.

With reference to the attached drawings, FIGS. 1-6, a device for thecreation of cavitation processes in fluid flows resulting in localizedregions of increased pressure, heat release and vigorous mixing togenerate changes in fluids are disclosed. The method and device includethe use of a flow-through hydrodynamic multi-stage cavitation reactor topromote chemical and physical processes and reactions that occur in ashort time and results in new products. Intense localized heat releasedbecause of gas compression and microjet formation, which accompany theimplosion of cavitation bubbles, excite molecules contained in vaporsand in the adjacent layers of surrounding fluid transiently enrichedwith the high-boiling point ingredient(s), thereby driving chemicalreactions and processes.

A preferred embodiment of the multi-stage cavitation device of thepresent invention is illustrated in FIGS. 1 and 2, which depict ahydrodynamic flow-through multi-stage cavitation device 10 capable ofachieving the objects of the present invention. Said device 10 comprisesa housing 12 defining a substantially cylindrical exterior having afluid inlet 14 and a fluid outlet 16. The fluid inlet 14 is positionedto introduce the fluid medium into the device 10. Between the fluidinlet 14 and the fluid outlet 16 are a series of chambers, as describedbelow, configured to create cavitational features in the fluid medium.The fluid outlet 16 directs the fluid medium from the device 10.

The cavitation device 10 as shown in FIGS. 1 and 2 is comprised of acylindrical body 12 made preferably of a metal, an inlet 14 and anoutlet 16. An inlet cone 18 is located in front of a multi-jet nozzle 20along the flow path. A guide cone 22 is positioned behind the nozzle 20and features spiral guides 24. The multi-jet nozzle 20 is shaped as adisk having a perimeter ring 20 a and features four channels 20 b thathave abrupt contractions and expansions across their width (FIGS. 5 and6). The number of spiral guides 24 is equal to the number of channels 20b in the multi-jet nozzle 20. The channels 20 b are uniformlydistributed throughout the surface area of the perimeter ring 20 a anddirect flow into a working chamber 26.

The working chamber 26 is located behind the multi-jet nozzle 20 alongthe flow path and has an inner wall formed by the guide cone 22 and anouter wall formed by a convergent cone 28. The convergent cone 28 isaligned coaxially with the guide cone 22. Behind the convergent cone 28is the vortex chamber or generator 30 comprised of disks 32, 34 withcurved flow guides 32 a, 34 a and central holes 32 b, 34 b (FIG. 4) thatare coaxially aligned. An annular gap 36 is located between the frontand rear disks 32, 34 and around a cylinder-type body 38 of slightlysmaller diameter than the vortex chamber 30. The curved flow guides 32a, 34 a are raised with respect to the disks 32, 34 so as to extend outto the cylinder type body 38. The body 38 blocks the direct path of thefluid flow jet emerging from the central hole 32 b in the front disk 32.

The flow guides 32 a, 34 a create multiple curved flow paths from thecentral hole 32 b in the front disk 32 to the annular gap 36 of thevortex generator 30. Similar paths are created from the annular gap 36to the central hole 34 b on the rear disk 34 on the backside of thecylinder-type body 38. The central holes 32 b, 34 b, the outlet of theconvergent cone 28 and an inlet of an atomizing cone 40, which issituated behind the vortex generator 30 along the flow path, all havethe same diameters.

The inventive cavitation device 10 can be made from many materials,although there are some constraints placed on them. The materials shouldbe simple in fabricating and brazing, be able to withstand both highpressure and high temperature, and exhibit high resistance to corrosion,thus allowing the system to be operated continuously and/or repeatedlywith a variety of fluids. The materials should be mechanicallycompatible to assure similar properties of material extension uponheating. A coating with alloys, electrodeposited layer(s), plastics,nanoparticles, nanodiamond, metals, catalysts and enzymes is possible.In one preferred embodiment of the invention, the device is made from ahardened stainless steel.

Both the inner and outer system dimensions depend upon the intended useof the device. A small-scale cavitation system is preferable when theamount of fluid to be processed is limited or its cost is too high. Alarge system with an inner diameter of ten inches or greater provides ahigh treatment throughput and may generate larger cavitation features.In the preferred embodiment, the cavitation device 10 is about fourteeninches long with an outside diameter of about three inches.

The present cavitation system provides at least three major cavitationzones and operates as follows. Presumably sufficient fluid is initiallypressurized with a proper pressure pump and introduced through the inlet14 which has a uniform outside diameter of one and one-half inches inthe preferred embodiment. The fluidic reaction mixture enters at the topof the inlet cone 18, which is surrounded by the inner peripheral wallof the housing 12. The fluid accelerates over the inlet cone 18 andmoves into the channels 20 b of the multi-jet nozzle 20. To enhancemixing and cavitation, the channels 20 b of the multi-jet nozzle 20 areuniquely shaped and contain both contractions 52 and expansions 54. Moreparticularly, the cross-sectional diameters of the channels 20 b varyalong the fluid path, as illustrated in FIG. 5.

As illustrated in FIG. 6, the channels 20 b can alternately befabricated as Venturi nozzles to separate vortices and generate pressurepulsations at characteristic frequencies. A Venturi nozzle is defined asa throttle device comprised of a conical inlet 56 with a round profile,a cylindrical throat 58 and a conical outlet (diffusor) 60. The Venturinozzle generates unsteady flow that can be calculated (Fedotkin andGulyi, 2000; Mahesh et al., 2004; Li et al., 2008).

When fluid moves through the channels 20 b, the vortices, completelydetached jets and possible cavitation are produced. They act upon thefluid by altering its properties. The streams exiting adjacent channels20 b are mixed by passing through the narrow gaps formed by the spiralguides 24 mounted between the guide cone 22 and the walls of theconvergent cone 28, and flowing through the working chamber 26.

Although this configuration is preferred, it should be understood thatthe spiral guides 24 do not have to be mounted at a specific angle or ata specific location relative to the channels 20 b in order to generatecavitation within working chamber 26. The preferred configuration of theguides 24 has a gradual decrease in the pitch of the spiral toward thepeak of the guide cone 22 in order to accelerate the flow velocity. Thisallows the fluid to form patterns and jets in the flow and form vorticesand shear when the flow's upper layers separate from those lyingunderneath because of the substantial difference in the velocities.

The fluid directed by the guides 24 exhibits significant cavitationwithin the working chamber 26. Implosion of the generated cavitiesresults in the formation of shock waves, high-velocity local jets andheat dissipation, improving both reaction rates and mass transfer(especially during the acid pretreatment and alkaline delignification).The jet velocities and intensity of the vortices and cavitation dependon the interaction of a fluid-vapor mixture with vapor. As thecavitation number decreases, fluctuating cavities with periodic vortexshedding, fluid-vapor filled cavities within a turbulent wake, andcavities filled with vapor are observed. In the cavitation region,strong momentum transfer between the higher and lower flow layersoccurs. In the core zone of the region, the flow velocity is high andevenly distributed. The low velocity region lessens as the flow pathmoves downstream. The cavitation bubble dimensions and the intensity ofthe cavitation field both increase as the fluid moves toward the middlepart of the working chamber 26. An increase in the difference in flowpressures favors cavitation and vortex formation.

The cross-sectional area of the working chamber 26 decreases along theflow path due to the decrease in diameter of the guide cone 22, and thecorresponding diameter of the convergent cone 28 resulting inacceleration of the fluid flow. With the increase in velocity the fluidpressure drops, favoring conditions suitable for cavitation. Moreover,upon exiting the working chamber 26, the fluid is further accelerated bysliding over the spiral guides 24. The fluid then passes into the vortexchamber 30 through the central hole 32 b in the front disk 32, entersthe flow guides 32 b and passes to the annular gap 36. The fluid thenfollows the flow guides 34 a of the rear disk 34 to the central hole 34b. The drastic increase in the cross-sectional area of the flow path,sharp changes of the flow direction and vigorous vortex formationpromote nucleation, growth and coalescence of cavitation features. Inthe vortex chamber 30, the cavitation bubbles are subjected to theincreased pressure caused by flow dynamics, i.e., apparent centrifugaland Coriolis forces. Consequently, the bubbles implode at a higher flowvelocity than normal.

Near exiting the vortex chamber 30, the fluid, which has been heated bythe cavitation process, enters the channels formed by the guides 34 aand accelerates due to the narrowing cross-sectional area. When fluidmoves along the curved channels, it causes rolling friction, whichrequires much less force to overcome than sliding friction. The flowguides 32 a, 34 a of the disks 32, 34 of the vortex generator 30 areshaped as curved arcs of circles in order to reduce the energy requiredto direct fluid in the vortex generator 30. The energy required to forceflow along the convex section of the curved guides 32 a, 34 a is muchless than with straight guides. The force required for overcoming therolling friction on the concave section of the guides 32 a, 34 a dependson their curvature.

The vortex flow exits the central hole 34 b in the rear disk 34 andatomizes within the cone 40. The drastic increase in cross-sectionalarea, sharp alterations of the flow direction and its vortex naturepromote formation and expansion of cavitation features and othereffects. In the outlet 16 from the atomizer 50, the flow rate drops withminimal energy loss until it reaches the level acceptable by thedownstream pipe line safety requirements. As the hydrostatic pressurerises, the cavitation bubbles quickly collapse and the negative impactof cavitation on the downstream pipe line and equipment promptlydisappear. The flow-through cavitation process may be coupled withUV-Vis-IR light treatments to improve efficiency. The fluid may also beirradiated with sound or ultrasound waves prior to, during and/or afterthe flow-through cavitation treatment.

The present multi-stage cavitation device 10 provides at least threezones where vigorous vortex formation and intense cavitation occur. Thefirst cavitation zone is within the working chamber 26, the secondcavitation zone is in the vortex generator 30, and the third cavitationzone is in the atomizing cone 40. This configuration is particularlycost efficient in a large volume treatment. However, the same principlescan be applied to any alteration at smaller scale. Note, that ultrasonicradiation generating devices are not sufficient to induce uniformcavitation in large vessels.

The device 10 schematically presented in FIGS. 1-6 is used for carryingout the method, according to the present invention. FIG. 7 illustrates aflowchart of the inventive processes for extracting carbohydrates frombiomass and converting said carbohydrates into bioalcohol. The process70 begins with the step of first biomass preparation 72 a.Traditionally, bioalcohol is produced following either dry or wetmilling processes. The first biomass preparation 72 a includes washing,drying, chopping and/or grinding the biomass material to remove unwantedcontaminants and reduce its particle size. The biomass is preferablylignocellulosic biomass—available mainly as agro-waste or forest-waste.Typical biomass materials include hops, corn cob, corn stover, cottonstalk, wheat straw, rice straw, sugarcane bagasse, switchgrass, poplarwood, sorghum straw, and water hyacinth. Preparation 72 a usingtraditional dry milling processes typically includes separation ofunwanted parts, i.e., roots, etc., and then chopping or grinding intosmall pieces. Wet milling processes would include washing with water anddrying at about 50-60° C. Dry milling processing may also includewashing and drying prior to the chopping stem, but this involves anadded expense and is not typically done for dry milling. The desiredsize of biomass pieces is typically between 1 mm to 5 mm, but must beconformed to the particular cavitation device and its variousconstrictions so as not to choke any flow path by accumulation ofparticles. The prepared biomass is then stored in a hopper or similarcontainer 73 until it is ready to be subjected to further processing. Ifthe biomass material is a grain, the ground grain powder is combinedwith a fluid carrier, such as water, to make a grain-based liquidmedium, which can be in the form of a slurry. Grains can include corn,rye, sorghum, wheat, beans, barley, oats, rice, or combinations thereof.

As illustrated in FIG. 29, the wet milling process 72 a enables severalend products to be obtained. Water 95 is added to fresh biomassmaterials 93 and mixed to form a slurry 97. This slurry is conveyed by apositive displacement pump to a homogenizer 99, where the mechanicalforces cause the gluten particles to agglomerate. The shearing forceswhich occur in the process break down the gluten-starch matrix. Thedough is conveyed via a buffer tank 101 to a decanter 103, whichoperates using three process stages: washing, classifying andconcentrating. In the initial process stage, a separator 105 enables theproduct to be separated into starch and other flour constituents, inparticular A-starch and gluten 107, and B-starch and pentosane 111.A-starch and gluten 107 are extracted separately and can be processedinto other end products 109, while pentosane and B-starch 111 aretransferred to biomass storage 73 and used for bioalcohol production 70.

Continuing with the extraction of carbohydrates, a first biomasssolution is mixed 74 a containing the prepared biomass and reagents. Thereagents include water and an acid or an alkali, as well as, othersupplementary chemicals. The water is preferably demineralized. Themixture is usually prepared in a tank of suitable dimensions preferablyprovided with suitable agitation, i.e., a pitched blade turbine orsimilar operated at about 100-500 rpms. The tank is filled withdemineralized water and the processed biomass is added from its hopper.The proportion of biomass to water is determined by weight orvolume—typically 5-50% w/v. Either an acid (H₂SO₄) or an alkali (NaOH)is added in required proportions by percent volume of water. For acidthe range is 1-5% v/v. The alkali may be added to form a solution ofsimilar strength. The solution is preferably thoroughly agitated toachieve a well-blended solution.

The first biomass solution may optionally be subjected to autoclaving,steam explosion or heat treatment 76. Autoclaving or steam explosion isby heating to about 120° C. under 15 psi steam pressure. Heating underpressure results in thermal expansion of the biomass, which increasesits porosity. Such expansion is helpful in faster diffusion of enzymemolecules through the biomass matrix and provides easier access to thecellulose portion of the biomass. Heat treatment is simple heating to atemperature of about 100° C.

If the heating step 76 is carried out under acidic conditions, it alsoresults in acidic hydrolysis of the hemicellulose portion of thebiomass. This releases a significant amount of pentose sugars likexylose. Some of the cellulosic portion may also get hydrolyzed torelease hexose sugars if the acid concentration is sufficiently high.Some similar hydrolysis will also occur during alkaline treatment, buton a much smaller scale. After acid treatment, the biomass is filteredout and washed thoroughly before subjecting to alkaline pretreatment.Alkaline pretreatment results in removal of the lignin layer thatexposes the hemicellulosic and cellulosic portions of the biomass toenzyme action. The biomass may again be stored after heat treatment 76,but must be frequently agitated to avoid settling of biomass particles.

The solution—either with or without the heat treatment process 76—isthen subjected to a first hydrodynamic cavitation treatment 78 a using adevice similar to those described elsewhere herein. A slurry pump ofsuitable capacity must be used and the biomass solution is preferablyrecirculated through the hydrodynamic cavitation device using a holdingtank. For this stage of cavitation processing, the slurry pumppreferably has a discharge pressure of about 500 psi or 35 bar. Thetemperature of the solution will rise as it is processed through thecavitation device, which provides additional heat treatment. Hydrolysisof hemicellulose and cellulose occurs during this first cavitationtreatment 78 a. A large portion of the carbohydrates are extracted fromthe biomass by an acid or alkali hydrolysis process, which process isaided by the hydrodynamic cavitation. Strong microturbulence generatedby hydrodynamic cavitation helps in the faster and more efficienttransport of sugar moieties out of the biomass matrix into the solution.The time and intensity of the treatment 78 a depends upon the biomass. Atypical treatment 78 a of about 30 minutes should be sufficient toremove all sugar released from hydrolysis.

The cavitated biomass solution is sent to a settling tank and subjectedto a first filtration process 80 a using suitable filters to separatethe biomass from the solution containing the extracted carbohydrates.The first filtrate containing the extracted carbohydrates, typicallypentose sugars—is sent to a first holding tank 82 a for laterfermentation. The filtered biomass is subjected to a second biomasspreparation process 72 b, wherein it is again washed, preferablyrepeatedly to remove all acid and alkali, and then dried and stored forfurther enzymatic hydrolysis.

The second processed biomass is then combined with enzymes,water—preferably demineralized—and other chemicals to form a secondbiomass solution 74 b. The solution of biomass and demineralized wateris prepared in a concentration of about 10% w/v. The enzymes maycomprise commercial Cellulase enzymes, or microbes (i.e., Bacillusamyloliquefaciens or Bacillus subtilis) or fungi (i.e., Trichodermareesei) that release such enzymes. In the case of commercial enzymes,they may be added to the biomass solution. In the case of microbes orfungi, an inoculum along with supplementary nutrients may be added tothe biomass solution. The pH of the solution is preferably adjusted to apre-determined value using buffer solutions or the addition of simpleacids (H₂SO₄) and alkalis (NaOH). In the case of commercial enzymes, theoptimum pH is already provided by the supplier. For microbialhydrolysis, some experimentation is needed to determine the optimum pH.This second biomass solution 74 b is also agitated during mixing asdescribed above to prepare a well-blended solution.

Generally, this process is called liquefaction. In the grain dry-millingprocess, the liquefaction process follows heat treatment, at which pointenzymes are added to the grain-based liquid medium in order to breakdown the starch polymer. The liquefaction process is followed by asaccharification process in which other enzymes are added to thegrain-based liquid medium. The enzymes in the saccharification processcreate a sugar mash that can be transferred to a fermentation processwhere yeast can convert the sugars into carbon dioxide and alcohol.

This second biomass solution is then subjected to a second hydrodynamiccavitation treatment 78 b to extract further carbohydrates by enzymatichydrolysis. The conditions of this second cavitation treatment 78 b aremuch milder than the conditions of the first cavitation treatment 78 a.This is because the enzyme molecules or microbial cells are delicate andcan be easily denatured or disrupted due to the shockwaves produced bycavitation bubbles or high shear stress in the flow. While a slurry pumpis again used, the discharge pressure should be small—typically in therange of 50-150 psi. In this second hydrodynamic cavitation treatment 78b, the cavitation device is operated essentially to provide convectionin the flow to enhance the transport of enzyme molecules in the biomassmatrix and their access to the cellulose in the biomass. Such secondcavitation treatment 78 b preferably continues or is recirculatedthrough a holding tank for about 30 minutes.

The second cavitated biomass solution is then subjected to a secondfiltration process 80 b to separate the biomass from the hydrolyzate,i.e., solution containing the extracted carbohydrates. The secondfiltrate containing additional extracted carbohydrates—typically hexosesugars—is sent to a second holding tank 82 b. The remaining filteredbiomass may be stored for further use as fuel, cattle feed or otherintended uses.

The first and second filtrates 82 a, 82 b, may be stored in separateholding tanks or the same holding tank. In further processing, the firstand second filtrates 82 a, 82 b are subjected to fermentation processes84 a, 84 b using suitable bacterial species to produce the bioalcohol.The fermentation processes 84 a, 84 b may be performed separately ortogether, i.e., as a single process. Whether fermentation is performedas a single process or two separate processes depends upon therequirements of the facility. Following fermentation, the alcohols maybe separated from the broth by standard distillation processes.Alternative processes to distillation include in-situ product recoveryand removal using techniques such as liquid-liquid extraction or gassparging.

When stored in holding tanks, the first and second filtrates 82 a, 82 bmay contain residual starches, dextrins and proteins. Intensehydrodynamic cavitation treatment, as performed in process steps 78 aand 78 b, promotes hydrolysis of starchy substances in their interactionwith enzymes. As shown in the alternate processing illustrated in FIG.28, the first and second filtrates 82 a, 82 b may be subjected tohydrodynamic cavitation treatment 86 a, 86 b during transport fromholding tanks to the fermentation apparatus 84 a, 84 b. This additionalcavitation treatment 86 a, 86 b is mainly designed to increase the sugarcontent of the first and second filtrates 82 a, 82 b. After thecavitation treatments 86 a, 86 b, the first and second filtrates 82 a,82 b continue onto the fermentation processing 84 a, 84 b.

Typical fermentation processing 84 a, 84 b lasts from about 72 to 96hours. The hydrolyzate or filtrate 82 a, 82 b may be supplemented withnutrients for the growth of a microbial culture. Typical bacterialspecies includes Escherichia Coli, Saccharomyces cerevisiae, Zymomonasmobilis, and Lactobacillus buchneri. All of these species can consumeboth hexose and pentose sugars. Mixed sugar consumption is enhanced ingenetically modified species. Use of such genetically modified speciesfacilitates the simultaneous fermentation processing 84 a, 84 b of bothfiltrates 82 a, 82 b containing mainly pentose and hexose sugars,respectively. These species produce bioethanol. For biobutanol, onewould use species Clostridium acetobutylicum, which is an anaerobicspecies. Many genetically modified versions of this species are alsoavailable.

In the course of fermentation, sugars penetrate into microbial cells,where they are involved in the chains of enzymatic processes that leadto the formation of alcohol and carbon dioxide. The fermentation processresults in the production of bioalcohol, containing alcohol, water andsolids. Apart from alcohol and carbon dioxide, by-products and secondaryproducts are formed during the fermentation. Secondary products includeall substances (other than carbon dioxide and alcohol) that result fromyeast fermentation of sugars, such as, glycerine, acetic aldehyde, acidsand others. By-products are not formed from sugars and other substancescontained in the bioalcohol. The most important by-products are fuseloils, which are mainly formed during the multiplication of yeast.

Apart from ethanol, bioalcohol contains various organic and inorganiccompounds: sugars, dextrin, minerals, volatile compounds (esters,alcohols, aldehydes, acids), etc. The composition and content ofimpurities depends on the type of material, its quality, and processingmodes during the technological process. To reduce the content ofimpurities and increase the yield of ethanol, the bioalcohol undergoesadditional hydrodynamic cavitation treatment 85 a, 85 b before furtherprocessing. The cavitation treatment 85 a, 85 b of the bioalcoholresults in the destruction and chemical conversion of complex substancesand compounds. Dextrin and sugars remaining in the bioalcohol afterfermentation 84 a, 84 b are converted into ethanol as a result ofchemical reactions in the presence of enzymes and intensification ofmass exchange processes. Following this additional cavitation treatment85 a, 85 b, the alcohols are separated from the broth by standarddistillation 87 or similar processing.

The product resulting from the distillation process 87, contains ethanoland impurities such as water, acetaldehyde and/or acetal, benzene,methanol, fusel oils (such as isobutyl, isoamyl and active amyl),non-volatile matter, heavy metals and others. Ethanol containing theseimpurities above the specified concentrations cannot be used inmedicine, pharmaceutical and food industry, for example for productionof alcoholic beverages. Alcoholic beverages made from ethanol containinga large amount of impurities have poor taste quality and a strong smell.Distillation, molecular sieving, and other purification techniques areused to separate these impurities and produce more pure ethanol. Thesemethods require a large amount of energy and expensive equipment.Ethanol having a higher purity may be obtained by further hydrodynamiccavitation processing 89 after distillation. Such additionalhydrodynamic cavitation treatment 89 eliminates the need for multipledistillation and multistage filtration to produce higher purity ethanolwith the necessary consumer characteristics. Cavitation treatment 89 ofthe bioalcochol obtained after primary distillation 87 results in thedestruction of impurities, precipitation of heavy metals, improved tasteand reduction in the strong smell of bioalcochol. Bioalcochol subjectedto cavitation processing 89, can be used to produce food quality alcohol91 without additional complex purification.

In accordance with the present invention, the fluidic reaction mixtureis treated either continuously or periodically, by passing through anyof the cavitation devices disclosed herein. The devices can be placedanywhere in a production site or any other body. Another design existsin which the device may be fixed in position or movable. In addition,multiple devices may be combined in a series or parallel configuration.In practice, it is necessary to take into account the cost of thedevice, its production capacity and the energy, maintenance andoperation cost. It should be emphasized, that an operator of thehydrodynamic cavitation device is not required to wear high performancesafety products for hearing protection, such as earmuffs or earplugs, aswould be in the case of high-frequency cavitation.

The cavitation devices are static, i.e., contain no moving parts, andare configured for operation at a set fluid velocity and pressure offluid medium. As described below, the changing of chamber diameters andsurface features within the devices causes the generation of cavitationfluid features, i.e., bubbles. The subsequent collapse of the cavitationbubbles results in the localized elevations of pressure and temperatureand drives the extraction process at a higher rate to achieve a higheryield than other processes.

When fluid is subjected to the consecutive multi-stage cavitations it isheated up and becomes enriched with bubble nuclei. This lowers thedownstream cavitation threshold, intensifies processing and allowsselective chemical reactions to occur while targeting compounds ofinterest. This makes the present device unique and especially suitablefor treatment of multi-component fluids such as, for example, mixturesof biomass with water, acids or bases.

The flow-through cavitation devices are preferably multi-stageapparatuses whereby components are manipulated through localized highpressure and temperature impulses and advanced gas phase to solid/liquidphase transfer principles. Hydrodynamic cavitation assumes formation ofvapor bubbles within a fluid accelerated to a proper velocity. Inpractice, cavitation is achieved by forcing fluids into the flow-throughhydrodynamic cavitation device accelerated with a high-pressure pumpand/or by reducing the available flow cross-sectional area at constantpressure. The faster the flow rate, the lower the cavitation number. Alower cavitation number (especially cavitation numbers less than 1)equates to a higher degree of cavitation. The preferred embodiment ofthe present invention optimizes the cavitation to achieve the highreaction yield by applying the most suitable pump pressure selected froma preferred range of 25-5,000 psi. If too much energy is applied or thetreatment time is too long, then the cost goes up. By applyinghydrodynamic cavitation at a pump pressure designed to causealcohol-filled bubble formation and chemical conversion consistentlythroughout the fluidic reaction mixture, proper changes take place and adesirable outcome is achieved.

The present invention uses energy released upon the implosion ofcavitation bubbles to carry out mass transfer processes. Hydrodynamiccavitation is the phenomenon of the formation of vapor cavities in aflow of fluid, which is followed by the bubble collapse in a downstreamhigh-pressure zone. In practice, the process is carried out as follows.The fluid flow is pumped into the cavitation device. In a constriction,the flow accelerates causing the pressure to drop. This pressure dropresults in the formation of bubbles filled with the vapors of volatilecompounds that boil under the given conditions, i.e., a cavitation zone.When the cavitation bubbles move beyond the boundary of the low-pressurezone, the pressure in the flow increases and the bubbles collapse,exposing the vapors found within them and the surrounding liquid layerto localized high pressure and temperature, shearing forces, shockwaves, acoustic vibration and electromagnetic irradiation. Eachcavitation bubble serves as an independent mini-reactor, in whichchemical reactions and/or mass transfers occur, particularly at thevapor/liquid interface. The localized pressure and temperature aresignificantly higher than those found in many other industrial processeswhere the overall pressure and/or temperature may be increased ratherthan on a localized scale. The alteration of fluid composition resultsfrom the chemical reactions taking place within the collapsing bubblesand/or in the adjacent layers of fluid.

The phenomenon is named cavitation, because cavities form when the fluidpressure has been reduced to its vapor pressure. The vapor bubblesexpand as they move and suddenly collapse, creating a region of highpressure. The occurrence of cavitation bubble implosion is accompaniedby the formation of numerous deformed micro bubbles. The pressure andtemperature of vapors contained in these bubbles are very high. As fluidenriched with these micro bubbles moves into a reduced pressure zone,the micro bubbles become nuclei, which are less stable than thoseoriginally present in the fluid, and expand. The cavitation bubblesdeveloped from these nuclei enhance the cavitation field intensity. Thecontinuous process of bubble multiplication, expansion and implosionlowers the cavitation threshold because cavitation bubbles grow from thevapor nuclei, whose volume is larger than that of the naturally presentnuclei. The sudden collapse causes tremendous localized increases inpressure and temperature and intense shearing forces, resulting in highyield chemical reactions. By subjecting the fluidic reaction mixture tohydrodynamic cavitation, reagent molecules are activated and areconverted into new products.

The fluid directed through the device exhibits significant cavitation.The cavitation features created in the fluid flow include vapor bubblesof volatile components. As the velocity of fluid flow increases, itspressure drops. As the fluid pressure may drop below the vapor pressureof certain more volatile compounds, those compounds can form vaporbubbles. Those of ordinary skill in the art understand that morevolatile components have boiling points significantly lower than theboiling points of other less volatile components that may initially bepresent or produced in the course of treatment. Given thesesignificantly lower boiling points, the more volatile components willmore readily form vapor bubbles at the reduced fluid pressures in thecavitation device than other less volatile components. The cavitationprocess may also create vapor bubbles from air or other gasses trappedin pockets or cavities along the inner surface of the device.

The processing is dependant upon the physical properties of the fluidbeing processed and the energy requirements based upon ambientconditions necessary to generate cavitation in the fluid. It is wellknown that the complex liquid mixture comprised of different chemicalcompounds can be separated into pure fractions by heating it to thetemperature at which the individual fractions will evaporate (theprocedure is called atmospheric fractionation distillation). Generally,the compounds can be efficiently separated by, for example,fractionation distillation at a pressure of 1 atm, if the difference intheir boiling points is at least 25° C. Thus, there is no doubt thatmore volatile components will boil first under the conditions describedin the proposed invention. These first boiling components form bubblesfilled with vapors for providing increased contact area between theliquid oil and the gaseous alcohol for improved processing.

Implosion of the generated cavities results in the formation of shockwaves, high-velocity local jets and heat dissipation, improving bothmass transfer and reaction rate. As the cavitation number decreases,fluctuating cavities with periodic vortex shedding and vapor-filledcavities are observed. In the cavitation regions, strong momentumtransfer between higher and lower flow layers occurs. The cavitationbubble dimensions and the intensity of the cavitation field increase asthe fluid moves through the cavitation device. An increase in thedifference in the flow pressures favors cavitation and vortex formation.

In the case of a cavitation treatment of a multi-component fluid, thecomposition of the cavitation bubbles differs from that of the fluid.The bubble composition is enriched with the vapors of the compounds thatare volatile under the given conditions. The bubble implosion releasesenergy that drives chemical reactions and/or heats the fluid. Theprocessed mixture contains the products of these reactions, i.e., thenewly formed compounds. The size of cavities depends on the nature ofthe fluid under treatment, the engineering design of the cavitationdevice, and other conditions, such as the velocity of flow sustained bya pump. The pump pressure may be increased, as determined on acase-by-case basis, until a proper intensity of cavitation is achieved.In addition to determining the size, concentration and composition ofthe bubbles, and, as a consequence, the amount of energy released, theinlet pressure and device design govern the reaction outcome.

A practical approach to achieve the desired degree of cavitation is toestablish a pressure that provides enough bubble implosion energy formixing and carrying out the reactions. The optimal pressures producebubbles in sufficient quantities to achieve a high yield. However, asone skilled in the art would understand, different reaction mixturesrequire different energies obtained through cavitation in order fortheir products to form. Energy released because of bubble implosionduring a flow-through hydrodynamic cavitation process activatesmolecules forcing them to react and form new compounds.

From an overall point of view, the initial processing of the biomasssolution in the cavitation apparatus occurs at ambient temperature andambient pressure. No heat is added during the cavitation processing,although pre-heating may occur. The cavitation-assisted reaction is runat pump pressures between 25-5,000 psi, ideally at around 500 psi.

The cavitation apparatus creates conditions for a relativelyinstantaneous process due to the high-energy state of the gas-phasemolecules, vigorous mixing and the high reactivity of heatedsolid/liquid-phase molecules. Extraction of carbohydrates is completedin seconds or even faster than that after a single pass through thecavitation device, although multiple passes are possible.

It is important to note that the method of the claimed invention isdesigned to operate in a continuous manner as the fluid flow is pumpedthrough the cavitation device. Most prior art disclosures includecavitation systems that comprise batch or hybrid batch/continuoussystems. In such prior art systems, the reagents are introduced to thesystem and the reaction is allowed to proceed to equilibrium in aresidence chamber/vat. Once equilibrium is achieved, a portion of theproducts are removed from the system so that the remaining reagents andany subsequently added reagents may react to establish a newequilibrium. Such prior art processes require a long residence time, insome cases many hours, in order to produce the desired yield.

This is especially important in extraction processes such as this wherethe liquid in a solid/liquid interface around a particular area of thebiomass may become saturated with carbohydrates and prevent theextraction of further carbohydrates until the liquid is changed. Thehigher the concentration of products, i.e., carbohydrates, the slowerthe rate of extraction. This makes the prior art methods time consuming,expensive, and less efficient when compared to the claimed method with acomparatively faster extraction process with a high-yield.

Further, the prior art methods disclose a method wherein all componentsare present in the solid/liquid phases. In contrast, the generation ofcavitation features by the claimed process results in the formation oftransient gas bubbles comprised of volatile components to improve masstransfer and extraction of carbohydrates. This gas-solid/liquid reactionproduces a faster and greater yield over the solid/liquid reaction ofthe prior art batch systems. The inventors are not aware of anypreexisting teaching or disclosure of a similar gas-solid/liquidextraction process for the extraction of carbohydrates from biomass. Thegas-solid/liquid interface at the surface of each vapor-filled microbubble provides a very large interphase reaction surface, superiormixing, and allows for the prompt separation of products.

The present invention makes it possible to carry out acceleratedcavitation-assisted carbohydrate extraction processes by causing therepeated generation and subsequent collapse of cavitation bubbles. Theinvention also allows for the extraction of carbohydrates withoutconsuming large amounts of energy and avoids high-pressure operations.The present invention can extract carbohydrates and produce bioalcoholin a more efficient and more cost effective manner.

In a particular application of the inventive process, ethanol (proof195) was supplied to the inlet of the multi-stage cavitation devicehaving a configuration similar to the device depicted in FIG. 12 at apump pressure of 60 psi or about 4 bar with a flow rate of 220 l/min or58 gal/min. From the outlet of the multi-stage cavitation device theethanol was returned to the inlet pipe of the pump and through themulti-stage cavitation device 20 times. The analysis of ethanolprocessed in this way through the multi-stage cavitation device iscompared to an analysis of ethanol not processed using the hydrodynamiccavitation treatment. The tabular data in FIG. 30 shows that the ethanolprocessed in a multi-stage hydrodynamic cavitation device as describedherein has a lower concentration of 1-propanol, acetaldehyde and/oracetal, methanol, and total impurities. This level of purification wasachieved using only hydrodynamic cavitation without any furtherdistillation or other similar processes.

An alternate embodiment for the cavitation device, illustrated in FIGS.8 to 11, presents a cavitation device 10′ made of stainless steel andhaving a generally cylindrical shape. It is assembled of at least threeparts and is provided with threads at the outer surfaces of the inletand outlet ends for installation in line. Fluidic mixture is fed in tothe cavitation device 10′ with a pump operating at the pressure thatallows sustaining the selective generation of cavitation bubblescomposed of alcohol vapors. The fluidic mixture flows through a firstcylindrical passage 86 and enters a short downstream cylindricalpassageway 88 having a smaller diameter and connected to the firstcylindrical passage 86 with a conical opening 90. The fluid flow thenenters third and fourth cylindrical passages 92, 94 of progressivelylarger diameters.

The fourth cylindrical passage 94 has two cylindrical passage openings96 in its wall each interconnected to an inverted conical passageway 98.In addition, the fourth cylindrical passage 94 is provided with adownstream cylindrical impact pad 100 that has four segments ofcircumferential wall 102 on its top surface. (FIGS. 10 and 11) Thefourth cylindrical passage 94 and impact pad 100 are surrounded by anouter housing 104 that creates an annular chamber 106. The gaps 108between the wall segments 102 on the top surface of the impact pad 100connect the annular chamber 106 to an outlet chamber 110. The fluid flowexhibits turbulence when it encounters the bottom surface of the impactpad 100, accelerates passing through the two small openings 96 in thewall of the fourth cylindrical passageway 94, entering annular chamber106. The fluid flow then moves through annular chamber 106 towards thegaps 108 located between the four segments of the circumferential wall102 on the top surface of the impact pad 100 where the high-energy jetscollide and enter the outlet chamber 110 with a diameter that is smallerthan the diameter of the fourth cylindrical passage 94. As the fluidicmixture of biolipid, low molecular weight alcohol and catalyst movesalong the passageways of the cavitation device 10′, it undergoesmultiple cavitation events due to selective alcohol vaporization andsubsequent bubble implosion.

Another alternate embodiment for a flow-through cavitation device 90, asdepicted in FIGS. 12 and 13, is comprised of a steel housing 92, whichis attached to inlet 94 and outlet 96 pipes for direct connection to anindustrial pipeline (not shown). The device 90 preferably has a mirroredsymmetry such that from the inlet 94 to a mid-point 98 is repeated inreverse from the mid-point 98 to an outlet 96. The following descriptionwill follow the mirrored symmetry and describe from both the inlet 94and outlet 96 toward the mid-point 98 simultaneously.

Assuming flow from left to right, front and end disk multi-jet nozzles100 serve as the front and back walls of exterior working chambers 102and are located behind the inlet pipe 94 and in front of the outlet pipe96. The multi-jet nozzles 100 are equipped with constricting andexpanding channels 104 that are distributed uniformly over the surfacesof the disks that are the multi-jet nozzles 100. The working chambers104 are comprised of radial cones 106 and central guide cones 108, whichare attached to radial multi-jet nozzles 110. The radial multi-jetnozzles 110 feature both constricting and expanding channels 112. Thechannels 112 are spread evenly over the radial perimeter surface of thenozzles 110, which direct the flow to interior working chambers 114.

Flow guides 116 that direct the flowpath from the perimeter to a centerof the device 90 bound the chambers 114. The cross-section of the flowguides 116 generally has an S-shape configuration. A hemi-spherical body118 with a top niche 120 is mounted in the working chambers 114 againstthe multi-jet nozzle 110. The turbulizer disk 122 (FIG. 14) with curvedguides 124 and central hole 126 is located behind the guides 124 invortex chamber 128. The vortex chamber 128 is formed of the inner wallof the housing 92 and a cylindrical body 130 disposed in the center. Thevortex chamber 128 directs the flow from the hole 126 of the front disk122, around the cylindrical body 130 and out the hole 126 in the reardisk 122. The holes 126 in the front and rear disks 122 are coaxial.Their diameters are equal to that of holes in the guides 116. Themid-point 98 is within the vortex chamber 128.

FIG. 14 is a diagram that shows disks 122 with curved guides 124 andcentral holes 126. An interior side of the radial multi-jet nozzles 110is depicted in FIG. 15. The channels 112 let out into the workingchambers 114 housing the hemi-spherical body 118 with the top niche 120.FIG. 16 shows a cross-sectional view of the cylindrical body 130, whichis provided with the superficial perimeter guides 132 that serve as thechannels for fluid flow. FIG. 17 is a drawing of a preferred embodimentfor the guides 132 of the cylindrical body 130. FIGS. 18 and 19 depictthe junction between the working chambers 114 and the disks 122 andillustrate fluid flow. At the junction between the guides 124 and thedisks 122 are toroidal vortex chambers 134 which are connected to theholes 126 and working chambers 114. FIG. 20 is a simplified schematicillustration showing various embodiments for the niche 120: ahemi-sphere, a toroid, and a parabola.

The flow-through cavitation device 90 operates as follows. Fluid, forexample, a rough disperse emulsion, is pumped in the inlet pipe 94. Thefluid moves to the multi-jet nozzle 100 and passes through its channels104, which have both constrictions and expansions. Flowing through thechannels 104 causes the formation of vortices, detached flows andcavitation. Particles of the emulsion become subjected to shear forces,and emulsion quality improves. When cavitation bubbles reach the workingchamber 102 they pulsate and collapse. The bubble implosion results inincreased pressure and temperature and formation of local jets that acton the emulsion particles, further improving the emulsion homogeny. Thenthe flow moves in a converging cone formed by the radial cone 106 andthe central cone 108 that is mounted on the radial multi-jet nozzle 110.The flow is accelerated as it passes through the converging cone andthen enters the channels 112, which possess both constrictions andexpansions to generate vortices, detached flows and cavitation in thefluid flow.

After passing through the radial multi-jet nozzle 110, the flow movesinto the interior working chamber 114 where the cavitation bubblespulsate and implode. When fluid flow moves down along the surface of thehemi-spherical body 118 it falls off the sharp edges of the top niche120 generating toroidal vortices and a cavitation zone within the end ofthe working chamber 114. This cavitation field is characterized by ahigh intensity and a large cavity concentration. The end of the flowguide 116 is shaped as a constricting nozzle. The hole 126 in the disk122 is shaped as an expanding nozzle in the beginning and a toroidalresonator 134 is positioned in the constrict location.

When the fluid flows along the place of the attachment of the flow guide116 to the disk 122 it enters the ring grooves or toroidal resonator134. The working principle of the toroidal resonator 134 is based on ahigh sensitivity of an symmetric flow to a side pressure. Changingpressure at the jet origination point will result in angular alterationof the fluid flow. The fluid is forced off the toroidal resonator 134 bydiscrete portions, which generates dynamic pulsations, vortices andcavitation. The frequency of a toroidal resonator depends on itsdiameter (Agranat et al., 1987).

The flow moves out of the working chamber 114, accelerating due topassing through the hole 126 in the front disk 122 and then enterschannels located between the guides 124 on the front disk 122 in thevortex chamber 128. To maintain the fluid flow in a vortex state and toprevent it from moving in a plane parallel to the cavitator centralaxis, the guides 132 are provided on the cylinder 130 surface to directthe flow into channels 136 and sustain the spiral flow state. In thevortex chamber 128, cavitation bubbles are acted upon by centrifugal andCoriolis forces. As a result, the fluidic pressure rises and the bubblescollapse.

The direction of the flow moving down the channels 136 formed by theguides 132 provided on the cylinder 130 surface is determined by thepitch angle with respect to the central axis of the cavitation device90. In order to prevent flow from following the straight path, certainrequirements must be met. Lines that are parallel to the main axis andgo through any point on the surface of a guide 132 should intersect theadjacent guide 132. In FIG. 17, a straight line parallel to the centralaxis, goes through point a on the guide 132 and intersects the adjacentguide 132 at point b. The more guides that are intersected by a straightline (points c, a and b), the better the flow is twirled in the vortexchamber 128. The number of guides 132 that may be intersected by oneline is limited due to the requirement that the total area of the guidechannels 136 be equal to the area of the central hole 126 of the disks122. The total cross-sectional area of the channels 136 can becalculated by multiplying the number of channels by the height andwidth.

After passing through the channels 136 the fluid flow moves over thesurface of the vortex guides 124 and enters the hole 126 in the reardisk 122. This directs the flow along the central axis of the device 90.When the fluid flow passes the rear disk 122 and rear guide 116 itenters the rear toroidal resonator 134, the working principle of whichis described above. The accelerated flow falls on the top niche 120 ofthe rear hemi-spherical body 118, forming a pulsating toroidal vortexand cavitation zone (Dudzinskii and Nazarenko, 1996; Nazarenko, 1998).The pulsation frequency and the cavitation zone shape depend on thefluid properties, flow rate and the niche shape. The preferredembodiments for the niche 120 are described above.

The fluidic flow passes through the region of the toroidal resonator 134and niche 120 and enters the working chamber 114 bounded by the rearguide 116 inner wall and the rear semi-spherical body 118, whichtogether direct the flow from the central axis to the perimeter of thedevice 90. The cavities detached from the toroidal flow region implodein the working chamber 114. After passing the working chamber 114, thefluid flow enters channels 112 of the rear radial multi-jet nozzle 110provided with the constrictions and the expansions. This generatesvortices, detached flow jets and cavitation. When the fluid flow movesin the working chamber 102, the flow velocity decreases, the pressuregoes up, and pulsation and implosion of the bubbles take place. Then theflow passes through the constrictions and the expansions in the channels104 of the rear disk multi-jet nozzle 100 followed by generation ofvortices, detached flow jets and cavitation. The particles of emulsionthat undergo the cavitation process are reduced in size and theirsurfaces are modified. The cavitation bubbles pulse and implode withinthe working chamber 102, leading to shear force and local jet formation.Then the fluid flow exits the cavitation device through the outlet 96.

This preferred embodiment of the device provides at least elevencavitation zones: (1) the front multi-jet nozzle 100; (2) the front,radial multi-jet nozzle 110; (3) the top niche 120 in the fronthemi-spherical body 118; (4) the front toroidal vortex chamber 134; (5)the hole 126 and curved guides 124 of the front disk 122; (6) the vortexchamber 128; (7) the hole 126 and curved guides 124 of the rear disk122; (8) the rear toroidal vortex chamber 134; (9) the top niche 120 inthe rear hemi-spherical body 118; (10) the rear, radial multi-jet nozzle110; and (11) the rear-end multi-jet nozzle 100. The device designallows for two, four, six or even more mirror-symmetric cavitationregions. The plane of mirror symmetry goes through the mid-point 98 ofthe vortex chamber 128 located between the disks 122.

One of the numerous advantages of this embodiment is its versatility inrespect to fluid feeding. The device 90 can be connected to a pump ateither end and is especially suitable for technological applicationswith a demand for reversing flow direction. The device 90 can beincorporated in a pipeline without any risk of confusing inlet withoutlet. The main benefit of the present flow-through cavitation device90 is the interface of the vortex and cavitation generating zones withthe higher-pressure working chambers for the implosion of cavitationbubbles.

FIGS. 21 and 22 illustrate another alternate embodiment for aflow-through multi-stage cavitation device 140 that provides as many asten zones 142 for generation and collapse of cavitation bubbles and iscomprised of ten identical working chambers 144 and ten multi-jetnozzles 146 that differ in respect to the cross-sectional passage areascreated by their channels 148. When fluid is fed in the cavitationdevice 140 through a displacement pump or other means, the flow rate isthe same within the identical, sequentially located multi-jet nozzlechannels 148. Thus, it is possible to lower the fluid flow rate withinthe channels of nearby downstream multi-jet nozzles, while keeping thecavitation at the same level. When the fluid flow passes through thefront multi-jet nozzle 146 and the working chamber 144, the cavitiesimplode and the fluid's temperature rises. The increased temperature andamplification of the nuclei facilitate the onset of cavitation events indownstream cavitation zones 142. Therefore, the same cavitation numberand the same cavitation bubble concentration can be achieved withindownstream zones with the lower flow velocity inside the nozzle channels148.

During multi-stage fluid processing the hydraulic resistance is reducedby meeting the following condition: The cross-sectional channel area(S_(n)) of each multi-jet nozzle 146 is less than the cross-sectionchannel area (S_(n+1)) of the next multi-jet nozzle 146 along theflowpath, according to the equation: 1.0≦S_(n+1)/S_(n)≦1.1, where n=1,2, 3, 4, 5, 6, 7, 8 or 9. This save energy required for pumping a fluidflow through the multi-zone cavitation device 140. To scale back thecavitation device parts, for example, the multi-jet nozzle 146, it isnecessary to place the channels 148 for fluid passage as close aspossible. The number of the channels 148 of the multi-jet nozzle 146 islimited by the ratio of the total area of the largest cross-sectionalopenings (S_(d)) of the channels 148 to the surface area (S_(D)) of themulti-jet nozzle 146, such that S_(d)/S_(D)≦0.8, where

$S_{d} = {\sum\limits_{i = 1}^{k}\; S_{i}}$

(k is the number of channels of the multi-jet nozzle; S_(i)=πd_(i) ²/4,where d_(i) is the largest diameter of the channels I, and S_(D)=πD²/4,where D is the multi-jet nozzle diameter.

The present invention employs a specific process for extractingcarbohydrates from biomass and creating bioalcohol using hydrodynamiccavitation in fluids. The process involves flowing a fluidic mixturethrough the cavitation device having a specified inlet flow velocity andsystem pressure through acceptable piping and pumping means. The inletvelocity and system pressure vary according to the reaction mixtureproperties. The preferred flow rate is approximately ten gallons perminute, but may be adjusted lower or higher according to outputrequirements without affecting the results of the cavitation process.The preferred system pressure is 25-5,000 psi. In a particularlypreferred embodiment, the inlet velocity is ten gallons per minute andthe system pressure is about 500 psi.

The apparatuses and methods described herein, subject to the conditionsand specifications of usage, provide a method for extractingcarbohydrates from biomass and producing bioalcohol. The processing isdependant upon the properties of the fluidic reaction mixture beingprocessed and the energy requirements necessary to generate cavitationin the fluid.

The inventive method and cavitation device may be used in anycombination of single-pass, multi-pass, parallel flow, series flow, orother variations of deployment to render the desired result. As thisinvention applies to the chemical and physical nature of the processoccurring within the cavitation device, it also covers any array ofdeployment or fluid circuitry allowable by such device.

Thus, the disclosed method represents an advanced and highly optimizedapproach that allows completing extraction and conversion by applying aflow-through passage of the fluid medium through the hydrodynamiccavitation device. Apart from known methods, the proposed method'sefficiency is not a function of the degree of mixing but rather afunction of the unique gas-solid/liquid interaction conditions allowingthe high conversion rates and minimal residency time. The proposedprocess is based on the formation of short-lived gas bubbles comprisedof volatile components, their subsequent growth, pulsation, andcontrolled implosions within the solid/liquid phase. The cavitation isthe cornerstone of the present process, which consists of generatingcavitation by introducing the reaction mixture to a flow-throughcavitation device provided with the sequential compartments of varyingdiameters and inner surface features, reducing the pressure of fluidicmedium (reaction mixtures) such that it approaches the gas/liquidthreshold of the volatile components, and conducting the cavitation suchthat there is the generation of vapor bubbles followed by theirimplosion in high-pressure zones.

The present process significantly differs from all other known methodsby supplying the unique, previously unknown reaction conditions forconducting the advanced gas-solid/liquid extraction processes. Themethod allows for shorter reaction times and higher yields by creatingoptimal conditions required for the gas-solid/liquid processes toproceed to their completion. Since the transient gas phase isrepresented by the enormous number of short-lived alcohol vapor-filledmicro bubbles distributed throughout the fluidic reaction mixture, theproposed method provides a very large interphase reaction surface,superior mixing and the prompt separation of reaction mixture. Thehydrodynamic cavitation-assisted gas-solid/liquid processing ischaracterized with improved efficiency in comparison with other methods.

The proposed cavitation devices are particularly efficient at mixing thebiomass with reagents and generating in this mixture the transientcavitation features followed by separation of the reaction mixturecomprised of the extracted carbohydrates, residual initial reagents,remaining biomass, and other by-products. The flow-through hydrodynamiccavitation-assisted extraction processes can be carried out in-linerather than using time-consuming batch processing. An industrial scaledevice may allow large scale processing each day.

Numerical simulations of the cavitation described herein have beenperformed based upon a flow geometry having an orifice section 150similar to that depicted in FIG. 23. The inlet section 152 of theorifice has a diameter approximately twice that of the throat section154. The flow geometry of a nozzle or other constriction preferably hasa similar ratio of dimensions. The simulations were performed for an airbubble with incorporation of the turbulent fluctuations. The estimationof turbulent fluctuation velocity was performed using Kolmogoroff'shypothesis that the rate at which large eddies supply energy to thesmaller eddies is proportional to the reciprocal of the time scale oflarger eddies.

The gas bubbles may already be present in the liquid medium (i.e. water)or they may be small gas pockets trapped in the crevices in the wall ofthe conduit (or solid boundaries of the flow). As noted earlier, the gasbubble may also form in the flow due to release of the dissolved gas ator immediately downstream of the vena contracta, where the velocityincrease and the pressure decrease are at their extremes. If the bulkpressure of the flow at the throat of the constriction falls close to oreven below the vapor pressure of the solvent, localized evaporation ofliquid solvent is likely to occur resulting in formation of vaporbubbles. However, the vapor inside these bubble condenses rapidly withthe recovery of bulk pressure in the downstream region, and hence, thebubbles do not contribute much to the transient cavitation.

On a relative basis, the contribution of gas bubbles is higher than thevapor bubbles in the transient cavitation. One major assumption in thesimulations is that the bubbles are always at mechanical equilibriumwith the surrounding liquid. This means that the pressure inside thebubble is assumed to be equal to the bulk pressure in the surroundingliquid plus the Laplace pressure (2σ/R_(o)), where σ is the surfacetension of the liquid.

The numerical simulations essentially give a time history of severalparameters: bubble radius (R); velocity of the bubble wall (i.e. thetime derivative of the bubble radius); temperature inside the bubble;pressure inside the bubble; micro-turbulence generated by the bubble;and shock waves (or acoustic waves) generated by the bubble. Temperatureand pressure inside the bubble are representative of the sonochemicaleffect, while micro-turbulence and shock wave generated by the bubbleare representative of the sonophysical effect. In the present context ofbiomass pretreatment, the micro-turbulence and shock waves are ofrelevance.

The simulations were performed using permutation—combination of a fewmain parameters, namely: initial bubble radius, R_(o); ratio of orificeto throat diameters, β; and the cavitation number at the vena contracta,C_(i). Two representative values for each of these parameters werechosen, which are very similar to the actual values of these parametersin the inventive hydrodynamic cavitation device. These values are:R_(o)=50 and 100 microns; β=0.5 and 0.7; and C_(i)=0.8 and 1.0.Permutation—combinations of these parameters can result in up to 8 setsof values for simulations. Four sets were selected for simulations, theresults of which are shown graphically in FIGS. 13-16.

The graphs of FIGS. 24, 25, 26 and 27 represent various permutations ofoperation of hydrodynamic cavitation device for acid treatment (or acidhydrolysis) and alkaline treatment (or alkaline delignification). As faras enzymatic hydrolysis as well as fermentation of the hydrolyzatesobtained after acid pretreatment and enzymatic hydrolysis is concerned,it is carried out using enzymes (which are delicate protein molecules)and microbial cultures. The enzymes as well as microbial cultures aresensitive to transient cavitation. The shock waves generated bytransient cavitation as well as high shear rates prevalent in the bulkliquid flow at very high Reynolds number (corresponding to cavitationnumber ≦1) can denature the enzyme and disrupt the microbial cells.Therefore, we have provided some additional simulations at highercavitation numbers (>1) in which the cavitation bubbles undergo smallamplitude radial motion which is sufficient to generate low intensitymixing in the system to overcome mass transfer limitations, at the sametime not causing any damage to the enzymes and cells.

FIGS. 24A-24E present simulation data for R_(o)=100 microns, β=0.5, andC_(i)=1.0—with a pump pressure of 35 bar (or approximately 500 psi) anda recovery pressure of 8.5 bar. FIGS. 25A-25E present simulation datafor R_(o)=100 microns, β=0.7, and C_(i)=0.8—with a pump pressure of 35bar (or approximately 500 psi) and a recovery pressure of 17.5 bar.FIGS. 26A-26E present simulation data for R_(o)=50 microns, R=0.5, andC_(i)=1.0—with a pump pressure of 35 bar (or approximately 500 psi) anda recovery pressure of 8.5 bar. FIGS. 27A-27E present simulation datafor R_(o)=50 microns, β=0.7, and C_(i)=0.8—with a pump pressure of 35bar (or approximately 500 psi) and a recovery pressure of 8.5 bar. Thesimulation data presented in each of these graphs report radius ratio,temperature, pressure, shock wave, and microturbulence values over timeresulting from the simulated cavitation process.

The graphs of FIGS. 24A-27E show the generation of intensemicro-convection due to cavitation bubbles. This micro-convection hascontribution from high intensity shock waves—with pressure amplitude inthe range of 40 to 600 bar—and also strong microturbulence withoscillatory velocities in the range of 0.4 to 6 m/s. It is noteworthythat this extreme micro-convection is generated on an extremely smallspatial scale and is effective only in the close vicinity (˜1 mm) of thesurface of the bubble. Such convection is capable of generating strongmicro-currents of bulk liquid in the biomass matrix that help with theremoval of dissolved sugar and carbohydrate oligomers formed due tohydrolysis. Constant refreshing of the water in the biomass matrixenhances the rate of hydrolysis due to the fresh supply of hydrolyzingions inside the biomass matrix and also dissolution of sugar andcarbohydrate molecules leading to enhanced yield. The shock wavesgenerated by microbubbles also help in expanding or swelling of biomassthat increases the net voidage of the matrix allowing for smoother flowof liquid medium or water through the matrix.

For the use of the inventive hydrodynamic cavitation device inbioalcohol synthesis, these shock waves are highly instrumental inenhancing the kinetics and yield of acid and alkaline hydrolysis. Theshock waves not only cause depolymerization of lignin (induced by highlyenergetic collisions between the biomass particles) but they also helpgenerating intense liquid flow through the dense biomass matrix (due tothe microturbulence), which helps in effective penetration/diffusion ofOH— ions in the biomass matrix and removal of the monosaccharides formedduring hydrolysis. The shock waves essentially create a fine emulsion ofthe two phases with an enormous surface area (that is not typicallyachievable in a mechanically agitated device). This high interfacialarea provides increased mass transfer across the phases. Thus,hydrodynamic cavitation assisted acid pretreatment (or acid hydrolysis)and alkaline treatment results in higher yield and kinetics ofhemicellulose hydrolysis (and pentose sugar yield) and lignin removal ascompared to ordinary mechanically agitated devices. Transient cavitationalso helps in enhancing the kinetics of carbohydrate extraction as wellas the yield.

For two combinations of parameters, namely, β=0.5 and C_(i)=0.8, bothfor 50 and 100 micron bubbles, the flow was observed to flash at thevena contracta. This essentially means that due to a low cavitationnumber the bulk pressure at the vena contracta falls below the vaporpressure of the liquid. In addition, the turbulent pressure fluctuationssuperimposed over it take the pressure further down and caused rapidevaporation of the liquid in the bulk flow. The liquid phase thus didnot remain the continuous phase anymore, but became a dispersed phase inthe vapor of the solvent. The simulations model ceased at theseconditions.

For another set of parameters, namely, 13=0.7, C_(i)=1.0 for both 50 and100 micron bubbles, the turbulent pressure fluctuations were too weak tocause any remarkable growth of the cavitation bubbles that would resultin transient ensuing collapse. These set of conditions did not generatea transient cavitation effect sufficient to enhance or intensify theprocess.

The enzymatic hydrolysis and fermentation using hydrodynamic cavitationare to be carried out at milder conditions than those used for biomasspretreatment, namely, acid hydrolysis and alkaline delignification. Themilder conditions are generated by using a relatively lower dischargepressure of the throttling pump and also operating the reactor atcavitation numbers greater than 1. To signify the difference between thecavitation conditions created during biomass pretreatment and enzymatichydrolysis, some numerical simulations were conducted of cavitationbubble dynamics in the flow through constrictions, for example, as inchannel 20 b. These simulations essentially show stable oscillatorymotion of the cavitation bubble in the cavitating flow through similarnozzles. There are no strong physical characteristics associated with itsuch as generation of shock waves or microturbulence. The exactdimensions of a particular nozzle may be decided based upon the capacityof the overall unit (and may change with the capacity).

The flow geometry considered in such simulations was an orifice sectionas depicted in FIG. 23. The inlet section of the simulation nozzle had adiameter of 2 inches while the throat section had a diameter of 1 inch.The simulations were performed for an air bubble with incorporation ofthe turbulent fluctuations. For the estimation of turbulent fluctuationvelocity, we have used the Kolmogoroff's hypothesis that the rate atwhich large eddies supply energy to the smaller eddies is proportionalto the reciprocal of the time scale of larger eddies. The gas bubblesmay already be present in the liquid medium (i.e. water) or these may besmall gas pockets trapped in the crevices in the wall of the conduit (orsolid boundaries of the flow). As noted earlier, the gas bubble may alsoform in the flow due to the release of dissolved gas at the venacontracta, where the pressure falls to a minimum with velocity at itshighest value. If the bulk pressure of the flow at the throat of theconstriction falls close to or even below the vapor pressure of thesolvent, localized evaporation of liquid may also occur resulting information of vapor bubbles. However, the vapor inside these bubblecondenses rapidly with the recovery of bulk pressure in the downstreamregion, and hence, the bubbles do not contribute much to the transientcavitation. On a relative basis, the contribution of gas bubbles ishigher than the vapor bubbles in the transient cavitation. One majorassumption that we have made in our simulations is that the bubbles arealways at mechanical equilibrium with the surrounding liquid—in that thepressure inside the bubble is equal to bulk pressure in the liquid+theLaplace pressure (2s/R_(o)), where s is the surface tension of theliquid.

The numerical simulations essentially give a time history of severalparameters: (1) bubble radius (R), (2) the velocity of the bubble wall(i.e. the time derivative of the bubble radius), (3) temperature insidethe bubble, (4) pressure inside the bubble, (5) the micro-turbulencegenerated by the bubble, and (6) the shock waves (or acoustic waves)generated by the bubble. The simulations were performed usingpermutation—combination of 3 main parameters, viz. (1) initial bubbleradius, R_(o); (2) orifice to throat diameter ratio, β; and (3) thecavitation number at vena contracta, C_(i). Two representative values ofeach of these parameters were chosen, which are very similar to theactual dimensions of these constrictions in the hydrodynamic cavitationdevice. These values are: (1) R_(o)=50 and 100 microns, (2) β=0.5 and0.7, (3) C_(i)=1.2 and 1.5. Permutation—combinations of these parametersresulted in a total of 6 sets of simulations.

The results of the simulations clearly show the drastic change inbehavior of a single bubble when the cavitation number increasesabove 1. The bubble undergoes a small amplitude oscillatory motion andthe pressure and temperature inside the bubble stays close to ambient.There are practically no shock waves produced from the bubble nor anyintense microturbulence is observed. In such situation, the shear forcegenerated in the flow remains the only means of mixing. Since thevelocity of flow is rather moderate (in the range of 5-10 m/s), theshear stress is not strong so as to cause any adverse effect on enzymeas well as microorganism.

It is noteworthy that the shock waves generated from typical cavitationbubbles can cause disruption of the microbial cells as well asdenaturing of the enzyme. However, when the hydrodynamic cavitationdevice is operated at a cavitation number greater than 1, no suchadverse effect is seen. In this case, the sonochemical effect of radicalgeneration through transient collapse as well as sonophysical effects ofmicroturbulence or microjets is not seen. The hydrodynamic cavitationdevice in essence operates an efficient mixing unit for the enzymatichydrolysis or microbial fermentation that gives enhanced performance.The enhancement in enzymatic hydrolysis by cavitation is attributed tothe greater extent of enzyme/biomass interaction due to strongconvection in the medium, while faster fermentation (with concomitantlyhigher yield) is attributed to efficient substrate uptake-productrelease by microbes across cell wall and also efficient removal ofproduct gases such as CO₂ from the broth. In the case of aerobicfermentation, strong convection in the medium also assists efficientaeration of the broth due to the dissolved oxygen levels in the brothbeing maintained close to saturation throughout the fermentationduration.

Although several embodiments have been described in some detail forpurposes of illustration, various modifications may be made withoutdeparting from the scope and spirit of the invention. Accordingly, theinvention is not to be limited, except as by the appended claims.

What is claimed is:
 1. A process for increasing bioalcohol yield frombiomass, comprising the steps of: providing carbohydrates extracted fromthe biomass, wherein the carbohydrates contain residual starches,dextrins, and proteins; subjecting the carbohydrates to a hydrodynamiccavitation treatment so as to promote additional conversion of theresidual starches, dextrins, and proteins into carbohydrates; combiningthe carbohydrates with a bacterial species and nutrients to form afermentation fluid; fermenting the fermentation fluid to form abioalcohol solution; subjecting the bioalcohol solution to an additionalhydrodynamic cavitation treatment so as convert any remainingcarbohydrates into bioalcohol;
 2. The process of claim 1, wherein thebiomass comprises a filtrate of hydrolyzate containing pentose sugars,hexose sugars, or a combination.
 3. The process of claim 2, wherein thebacterial species comprises Escherichia Coli, Saccharomyces cerevisiae,Zymomonas mobilis, Lactobacillus buchneri, or Clostridiumacetobutylicum.
 4. The process of claim 1, further comprising the stepsof: distilling the bioalcohol solution so as to separate out bioalcoholand a fermentation broth; and subjecting the bioalcohol to a furtherhydrodynamic cavitation treatment so as to purify the bioalcohol forfood grade production.
 5. The process of claim 4, wherein the furtherhydrodynamic cavitation treatment of the bioalcohol destroys impurities,precipitates out heavy metals, improves taste and reduces a smell of thebioalcohol.
 6. The process of claim 5, wherein the impurities comprisewater, acetaldehyde, acetal, benzene, methanol, fusel oils, non-volatilematter, and heavy metals.
 7. The process of claim 2, wherein the step ofsubjecting the bioalcohol to a further hydrodynamic cavitation treatmentcomprises pumping the bioalcohol through a hydrodynamic cavitationdevice at a pump pressure of about 60 psi.
 8. The process of claim 2,wherein the step of subjecting the bioalcohol to a further hydrodynamiccavitation treatment comprises passing the bioalcohol through ahydrodynamic cavitation device at least twenty times.
 9. A process forextracting carbohydrates from biomass, comprising the steps of:preparing the biomass for extraction of carbohydrates; forming a firstbiomass solution comprising the prepared biomass, water, and acid or analkali; subjecting the first biomass solution to a first hydrodynamiccavitation treatment at an inlet pump pressure of about 500 psi, whereinacid or alkali hydrolysis of the biomass occurs; filtering the firstbiomass solution following the first hydrodynamic cavitation treatmentinto a first filtrate and an intermediate biomass, wherein the firstfiltrate contains extracted carbohydrates; creating a second biomasssolution comprising the intermediate biomass, water and an enzymesource; exposing the second biomass solution to a second hydrodynamiccavitation treatment at an inlet pump pressure of about 50 to 150 psi,wherein enzymatic hydrolysis of the biomass occurs; filtering the secondbiomass solution following the second hydrodynamic cavitation treatmentinto a second filtrate and a filtered biomass, wherein the secondfiltrate contains extracted carbohydrates.
 10. The process of claim 9,wherein the preparing step comprises wet milling the biomass, includingthe steps of: mixing fresh biomass with water; causing gluten particlesin the fresh biomass and water mixture to agglomerate; and separatingthe fresh biomass and water mixture into a first product comprised ofstarch and gluten and a second product comprised of starch andpentosane, wherein the second product is the prepared biomass.
 11. Theprocess of claim 9, wherein the biomass comprises hops, corn cob, cornstover, cotton stalk, wheat straw, rice straw, sugarcane bagasse,switchgrass, poplar wood, sorghum straw, and/or water hyacinth.
 12. Theprocess of claim 9, wherein the step of forming the first biomasssolution comprises mixing the biomass with demineralized water in aratio of 5% to 50% w/v.
 13. The process of claim 12, wherein the acidcomprises sulfuric acid in the range of 1% to 5% v/v and the alkalicomprises sodium hydroxide in the range of 1% to 5% v/v.
 14. The processof claim 9, wherein the step of creating the second biomass solutioncomprises mixing the intermediate biomass with demineralized water in aratio of between 5% to 25% w/v.
 15. The process of claim 14, wherein theenzyme source comprises cellulase enzymes, or microbes or fungi thatrelease cellulase enzymes, the process further comprising the step ofadjusting the pH of the second biomass solution to a desired pH for theenzyme source.
 16. The process of claim 15, wherein the microbescomprise Bacillus amyloliquefaciens or Bacillus subtilis and the fungicomprise Trichoderma reesei.
 17. The process of claim 9, wherein theextracted carbohydrates in the first filtrate comprise pentose sugarsand the extracted carbohydrates in the second filtrate comprise hexosesugars.